Photographic-printing process and apparatus therefor



E. K. HUNTER Filed Sept. 20. 1922 1 sheetssheet 1 Oct. 15, 1929.

PHOTOGRAPHIC PRINTING PROCESS AND APPARATUS THEREFOR Oct. 15, 1929- E. K. HUNTER PHOTOGRAPHIC PRINTING PROCESS AND APPARATUS THEREFOR Filed Sept. 20. 1922 14 Sheets-Sheet 2 Invent or. loyanmfi unn E. K. HUNTER Oct. 15, 1929.

PHOTOGRAPHIC PRINTING PROCESS AND APPARATUS THEREFOR Filed Sept. 20. 1922 l4 Sheets-Sheet Invervr:

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Oct. 15, 1929. E. K. HUNTER 1,732,049

PHOTOGRAPHIC PRINTING PROCESS AND APPARATUS THEREFOR Filed Sept. 20. 1922 14 Sheets-Sheet 4 will" III,-

Oct. 15, 1929. E. K. HUNTER 1,732,049

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PHOTOGRAPHIC PRINTING PROCESS AND APPARATUS THEREFOR Filed Sept. 20 1922 14 Sheets-Sheet 6 NMN MW NAN E. K. HUNTER PHOTOGRAPHIC PRINTING PROCESS AND APPARATUS THEREFOR l4 Sheets-Sheet 7 Oct. 15, 1929.

Filed Sept. 20. 1922 M a M W w PHOTOGRAPHIC PRINTING PROCESS AND APPARATUS THEREFOR Filed Sept. 20. 1922 1.4 Sheets-Sheet 8 Oct. 15, 1929. HUNTER 1,732,049

PHOTOGRAPHIC PRINTING PROCESS AND APPARATUS THEREFOR Filed Sept. 20. 1922 1 Sheets-Sheet 9 Oct. 15, 1929. HUNTER 1,732,049

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I PHOTOGRAPHIC PRINTING PROCESS AND APPARATUS THEREFOR Filed Sept. 20. 1922 14 Sheets-Sheet 12 262 Men/fir.-

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PHOTOGRAPHIC PRINTING PROCESS AND APPARATUS THEREFOR Filed Sept. 20. 1922 14 Sheets-Sheet l4 primarily Patented Oct. 15, 1929 UNITED STATES PATENT oFFlcE EDGAR KENNETH HUNTER, OF LONDON, ENGLAND, ASSIGNOR T0 JOHANNES ROBERT CARL AUGUST, OF LONDON, ENGLAND PHOTOGRAPHIC-PRINTING PROCESS AND APPARATUS THEREFOR Application filed September 20, 11522, Serial No. 589,365, and in Great Britain September 21, 1921.

The present invention relates to an improved printing process and apparatus therefor more particularly of the type in which symbols or other devices to be printed are established upon a reception element such as a metal sheet, cylinder or the like slab or lithographic stone by means of a photographic process operated b a light beam into the path of which a rep ica of the symbol is passed by a key or the like setting mechanism.

The present invention more particularly concerns control means for operating such processes.

According to the present invention the various steps of such a process including a spacing of the type, which as will be evident will be differential owing to varying widths of letter and forms thereof and including justifications, that is to say the variablespacing of words or other symbols forming a line of printed matter are controlled from a master strip of paper, card, metal, or other material, capable of being punched with holes or otherwise having its surface effectively altered so that it may co-operate with mechanical parts for the setting up and subsequent indexing of mechanism.

The elements of a machine operating according to such a series of a number of separate groups of "ariables, that is to say by way of example in the establishment for instance the printing of a letter such as Z the elements controlling this printing must be susceptible to at least two groups of variables and further movable according to a series in each group of variables, one variable thus forming two groups, whilst each group according to the Arabic alphabet will comprise a series of at least 26 letters.

Should it be desired for the machines to be capable of symbol printing as is required in the modern typography it must be further capable of instanteously setting up a further set of groups as is required by the large number of variable cases of type such as italic, roman, Arabic, script and the like. The selection of the particular element in the series of the particular group desired, and further, the manipulation of such groups as is desired by individual spacing and later on word justification in other controls are effected as above stated from a control strip. It is preferred to subdivide the effective area of such control strip into a plurality of unit area, the cutting away of any particular unit area consequently setting up means whereby any individual operation of the series or groups controlling the ultimate setting up of a symbol can be effected at any later time.

In the preferred form of construction of the machine, keys are provided either corresponding identically with the symbols ultimately to be set up for printing or according to some function thereof. The operation of these keys will then cause the operation of individual punches or the like elements deforming or otherwise altering the operative surface of a strip fed forward by space, that is to say the width of a unit area at each operation of the key, whether this be a spacing key or the key for a definite symbol, or again. the key of the selection of a group or of a series of any other one of the variable controlling the setting up of the symbol. Any suitable escapement means can be provided to feed the punch strip forward.

It is preferred that the symbols may be set up visually by the operation of the punching keys corresponding to them so that the operator will have before him a ready means of appreciating how far he has progressed in the establishment of a line of symbols. It is preferred also that some visual or optical indicating means will be provided so that he will also readily see as to what space will be left at the end of the line, so that he will be able to make the decision as to whether he will transfer a fresh word on to a fresh line or will include it in the line in which he is at that time operating.

The usual signalling means such as a hell or the like can be provided to indicate to him as to when he is entering upon the permissible stop length.

Having therefore operated a key for the establishment of a punched hole or the like in the operative control strip, the operation of a further key will determine the group such as the type of letter or keys, and again he may operate further keys as to the size of character.

The continuation of the set position of style, of character, size of character and the actual character automatically defines its spacing which is effected automatically when the group in the series have been selected or set up by the establishment of the keys cor responding thereto. At the end of any line of set up type, that is to say when the control strip has been punched with indicia corresponding to the symbols in other groups or series, justification of the words forming the line of type will be necessary. For each unit of spacing it is preferred to set apart a unit area of the punched strip so that when the end of a line is reached, the spacings between individual words forming that line can be automatically justified.

It is preferred however to arrange for a separate group of unit areas on the control strip at the end of each line so that master corrections can be made here to correct any error in the original setting up of a symbol or spacing.

lVhere the translation of the control strip is effected electrically, it is preferred that such correction means Will be arranged in series with the main setting mechanism so that the setting up of an element by one of the punchings on the control strip will only be effective that is not corrected by a punching on the particular master area of the said control strip.

The translation of the control from the control strip to the element setting up of the stencil symbols, spacing and the like, can be effected either mechanically by means of jacquard fins co-operating with the punchings in the strip or by means of electrical contacts Where the strip of insulating material allows for the passage of electrical brushes or the like contact elements through the punch holes or like punchings therein. These punchings whether affecting the operations either mechanically 0r electrically, preferably do so by step-by-step mechanism displacing the elements which they control, preferably through micrometric means. One type of micrometric means is set forth in my co-pending application United States Serial No. 602,47 5, filed Nov. 21, 1922.

By way of example the existence of a punching in a particular unit area on the control strip may move forward the stencil band in the light path either longitudinally or again laterally. The punching of the control strip may be performed either electromagnetically or mechanically by the operation of the eys.

The escapement for the carriage or the like carrying the matrix or the element receiving the light impressions such as a photographic or lithographic plate or film will be operated by micrometric control preferably operating step by step from a single punch perforation on the control strip.

In a convenient form of construction the source of light for obtaining a photographic image is arranged centrally to the stencil carrying the spindle rotatable around it into suitable position whilst the projection lenses are also rotatable around the source of light as also is the photographic film paper, metal sheet, cylinder or other element receiving the light beam for the formation of an image thereon.

If desired every operation or combination of the machine necessary for the selection of any particular symbol or its spacing or the spacing of groups of symbols or other justification has been set up as a. line may have a numeral assigned to it so that by establishing this numeral in the machine that operation will then be subsequently automaticallv performed. This numeral can be established by sets of keys one set for instance operating the setting up of numerals from 1 to 5, a second set multiples of 5 to 25, and a third set from 25 to 125 and so on, or again these numerals can be set up by keys the values of which are arranged in geometrical progression or other suitable series so that the setting up of any numeral by the keys of the machine will operate the ultimate setting up of the symbol of the desired form, spacing, size or other characteristic on the matrix or reception element.

This may be obtained by causing the operation of any key to select the particular area for the punching on the control strip so that the operation of a very few keys can operate a large variety of punching on the control strip and can consequently operate a very large variety of operations. v

The present invention is more particularly described with reference to the accompanying drawings in which Fig. 1 is a perspective view of the entire machine.

Figure 2 is a diagrammatic view showing a form of construction of operative table of a punching machine.

Figure 3 is a diagrammatic View of a photographic composing machine.

Figure 4 is a perspective rear View of a modified form of construction.

Figure 5 is a rear perspective view of the machine with the carriage and other parts removed.

Figure 6 is a front elevation of the carriage.

Figure 7 is a right hand end view.

Figure 8 is a corresponding left hand end view.

Figure 9 is a detail of the drive for the receiving film.

Figure 10 is an end view of part of the winding back mechanism for the carriage.

Figure 11 is a part sectional elevation corresponding to Fig. 9.

Figure 12 1s a diagrammatic plan view of the toggle displacement for the lens.

Fig. 13 is a detail view of a part of Fig 11.

Fig. 13 is a view of a part of the casing with the rock mechanism for the casing shaft 32.

Figure 14 is a perspective view on an enlarged scale of the automatic focusing mechanism, whereby the size of proJected character is determined.

Figure 15 is a detail View of means for altering the ratio of displacement of the carriage according to varying size of character.

Figure 16 is a corresponding side view.

Figure 17 is a perspective view of a part.

Figure 18 is a plan view of a setting mechanism.

Figure 19 is a sectional end view.

Figure 20 is a plan view showlng the carriage diagrammatically.

Figure 21 is a detail.

Figure 22 is a bottom plan view showing magnets on the carriage.

Figure 23 is an end view of a setting cam.

Figure 24 is a sectional view of one of the setting cams.

Figure 25 is a sectional end View of the pin element co-operating with the setting cams.

Figure 26 is an outside view of the pin element on the shaft.

Figure 27 is a view in perspective of the film.

Figure 28 is a plan View of the drums.

Figure 29 is a detail control drum.

Figure 30 shows the drive for the drums.

Figure 31 is a corresponding plan vlew.

Figure 32 is an outside elevation of the main control drum.

Figure 33 is a corresponding plan view partly in section.

Figure 34 is a sectional elevation on the line YY of Fig. 32.

Figure 35 is a detail.

Figure 36 is an outside view of the commutator drum.

Figure 37 is a view showing the control for the carriage magnets.

Figure 38 is an end view of a plug panel 36.

Figure 39 is an end View of the contact socket panel co-operating therewith.

Figure 40 is a plan view of the plug panel.

Figure 41 is a wiring diagram of the controller of Fig. 3639.

Figure 42 shows an example of the punch strip.

Figure 43 isa wiring diagram of the complete apparatus.

Figure 44 is a view on an enlarged scale of the commutator switch contact.

Figure 45 shows diagrammatically a justification means.

Figure 46 shows a modified form of line justification means.

'Figure 47 is similar to Figure 46 with the parts in another position.

Figure 48 is similar to Figures 46 and 47 but the parts in the justification position.

Figure 49 shows the connection of the justification means with the spacing means.

Fig. 50 is a perspective view of a stencil strip.

The principle and operation of the machine would be briefly described with relation to the form of construction shown in Figs. 1 and 2, in which 1 is an operating table having a plurality of keys 2, and slides 3, 4. An indicating mechanism is shown at 5.

The adjustment of an element in the slide 3 taken by way of example, caused the automatic selection of the style of type, that is to say either roman, Arabic script or the like. This type is in the form of a negative matrix or stencil on a film band 6, wound on and off the drums 7, 8.

As the photographic reproduction from the negative matrix or photographic stencil 6 can proceed automatically at a very much higher rate of speed than the operation of keys on a key-board corresponding to letters can be effected manually it will be desirable not to control the displacement of the negative matrix or stencil film 6 directly from the said keys 2, but rather through an intermediate control mechanism, which by this invention comprises an element such as a perforated strip 14 carried by rollers 9, 13 which may subse uently operate the necessary displacement o the strip 6 and like parts through electric selective mechanism, acquard mechanism or other like means. The displacement therefore, of the element Within the slide 3 will cause the punching of a slot or other indication on a strip within the casing 1, whilst the operation of a slide element 4 governing the size for instance, of the character within the group of the particular style selected will cause also a second indication to be punched on the said strip in pre-determined relation and grouping to the first punching. Similarly the depression of a key 2 corresponding to a particular letter or unit within the group or style will also operate a separate and individual punching in the strip.

The operation of the keys 2, not only causes a particular punch in the record strip, but also the setting up in visible character to the operator of the typed matter in the window 5", of the indicator 5, so that he will be aware as he approaches the end of a line of typed matter, and the amount of justification necessary in the spacing of the individual units or letters of the words and the words themselves. The operations of another key such as 2 will operate the punch of a further indication on the record strip to automatically later effect the necessary justification of the symbols, that is to say, the space through which the carriage must ultimately be fed between the successive exposures of characters.

Should any error have been made in the setting up of indications or punchings in the record strip 14 this can be corrected by the operation of further keys such as 2", which in a certain pro-determined area of the record strip also causes the operation of certain corrective punchings.

The record strip 14 then obtained from one or a number of operative tables 1 is passed from a drum 9 on which it is wound over a guide roller 10 and through a master control box 11. then through a control box 12, to be wound up upon another drum 13. The control boxes 11 and 12 are so arranged relatively to one another that the normal operative portion of the record strip 14 lies within the box 12 when its corrective portion lies within the box 11. The electro-magnetic mechanism operated by these control boxes are arranged in series with one another so that the mechanism of box 12 only comes into operation if not cancelled or corrected by box 11.

The record strip 14 therefore, by passage through boxes 11 and 12, causes firstly, the unwinding of the strip 6 until a certain area is reached, then displaces the strip within the area selected until a definite unit is reached and comes into the light path of a projection system 15, whereupon the focussing mechanism 16 is automatically operated by the record strip, due to the particular punching following the operation of the slide 4.

\Vith a view to avoiding the effect of inertia in the form of construction shown, the projection apparatus 15, with focussing mechanism 16 remains stationary, whilst the surface 17 upon which the character from the strip 6 is to be received is arranged within a light-tight casing 17, capable of rotation about a pivot whilst also the casing 18 carrying a drum 7, 8 is also rotated about the same pivot, so that therefore, in this case the drums 7, 8 will be wound or unwound respectively until a certain area is reached corresponding to a certain style, whereupon the casing 17 is oscillated about its pivot to bring from within this area a certain character on the strip 6 in the projection system 15.

The operative details of the machine according to the present invention will however, be more particularly described with reference to the modified construction shown in figures 3 et seq.

In this form of construction the negative matrix or film stencil 6 is mounted on a pair of drums 19, 20 (Figs. 27, 30) displaced together with the projection lens mechanism 21 relatively to the reee )tivc sheet or'receiving film wound on and o drums 22, 23 on a carriage 24, within a light-tight casing 25' (Fig. 3).

The stencil strip 6 in Fig. 50 is illustrated as having a series of characters arranged thereon, and it will be noted that portions of a gothic and an italic gothic alphabet are illustrated in sequence on this portion of the slrlp.

Receiving film caw'iagc and drive therefor The carriage comprises a pair of end frames 24 carrying guide rollers 26 running on rails 27 within the casing 25 (Figure 3). The carriage is connected by a cord 28 running over a pulley 29 on the inside of the casing 25 to a drum 30 (Figure 10) freely revoluble on its spindle. Adjacent to drum 30 is an electro-magnetic clutch 31 keyed to the driving spindle 32 so that whenever the clutch 31 is energized through the contact rin s 33 and brush connections 34 (Fig. 11), the rum 30 will be connected to the shaft 32 to wind the cord 28 upon it so as to displace the carriage 24 along the rails 27.

The main driving shaft 32 (Figures 6, 7, 8 and 12) is mounted in bearings in the casing 25 and on the outside of the casing passes freely through a pair of electro-magnetic clutch elements 35, 36. The electro-magnetic clutch 35 (Fig. 12) is solid with the casing 25 so that when it is energized, the shaft 32 will be locked rigidly in any position of adjustment. This shaft 32 has a flange 37 rigid on It between the electro-Inagnetic clutch 35 and the similar clutch element 36 loose on the shaft 32. The element 36 has a crank pin 38 through which it is connected by means of a connecting rod 39 with one end of a pivoted lever 40, the opposite end of which bears on a wedge or cam 41 mounted on a shaft 272, which is constantly reciprocating.

A pair of feathers (not shown) engage with the groove 32" in the shaft 32 and are kcved within bushes 45, 46, one having right hand ratchet teeth, whilst the other has left hand ratchet teeth, and which are respectively held up to a pair of correspondingly toothed sleeves 47 48 by springs 49.

The sleeve 47 has a pinion 5O driving an idler 5O meshing with the pinion 51 sliding on a key-way on a spindle 52 having a pin drive on the socketed end of the drum 23. Similarly the sleeve 48 has a pinion 53 driving an idler 53 meshing with a pinion 54 keyed on but slidable along a spindle 55, similarly provided with a pin drive to the drum 22 The spindles 52, 55 can be withdrawn against the springs shown by means of the hand-knobs 56 to release the rolls 22, 23 when desired.

It will consequently be seen that owing to the ratchet couplings 4547, 46-48, one

drum 23 will be rotated when the shaft 32 rotates in one direction whilst the other drum 22 will be rotated when the shaft 32 rotates in the opposite direction, but the driving drum for any particular direction of rotation can over-run the other when necessary.

The receptive sheet or receiving film 57 (Figure 8) has notched sides to engage with a pair of driving cog-wheels 58 sliding on but driven from the shaft 32.

Finally the carriage has a flange rail 59. This flange 59 is adapted to be periodically electro-magnetically clutched to a bar 60 periodically oscillated between set but variable limits, as will be hereinafter described in regard to Figs. 15 to 22, and 41.

A hand-wheel 61 is mounted on the end of the shaft 32 for hand operation when desired.

In the printing of successive characters on the sheet 57 by the photo exposure and development from stencll symbols or matrices on the sheet 6, it will be obvious that as each character has its own peculiar width so must the carriage 24 be displaced step by step by varying amounts relatlvely to the light path through the lens element 21.

At the commencement of a line therefore the margin of the column lies in the axis of the light path, and then after the character has been printed by being brought into the light path, the carriage 24 will be automatically fed forward not the whole width of the character space, but one half of this, and then at the establishment of the next character it will be automatically fed forward by the remaining half space amount and then, or simultaneously, as desired by an amount equal to half the letter spacing of the next letter to be established. This is effected in that (as hereinafter to be described) the bar 59 is displaced step by step by proper amounts according to the letters automatically set up in the light path.

Drive for optical projection system The optical projection system comprises a source of light 15, (Figure 1) a shutter 62 adapted to be operated by an electro-magnet 63 when the current is passed to this electromagnet from a main control switch drum to be hereinafter described. A projection lens 21 and the shutter 62 are mounted on a carrier 64 slidable on guides 65 rigidly mounted on the casing telescopic sleeves 66 connecting the light-tight casing 25 with lens carrier 64 and projection element 15. The carrier 64 has a threaded bush 67 on it engaging with a threaded spindle 68 carried in bearings of bracket 25 on the casing 25 and in a flange 69 on the bed-plate of the machine. The shaft- 68 has a wheel 68 on it driven from a worm 71 on a counter-shaft 7 2 having a wheel 73 driven from a shaft 74 lying parallel with the shaft 68 (Figures 3, 4, 14). The shaft 74 carries at its inner end a crown bevel wheel 75 (Figs. 3 and 4) meshing with a pair of bevel gears 76 on a pair of discs 77, 78, both loose on a cross shaft 79, but either of which can be coupled at will to the said shaft 79 by a pair of electromagnetic clutches 80, 81. The shaft 79 has a wheel 82 at its outer end driven by a motor 83 or otherwise from a source of power (Fi 3).

T e current is passed automatically either to the clutch 80 or 81 or cut off from either automatically from a main control drum, as will hereinafter be more particularly described.

Differential adjustment of optical elements It will be obvious that to obtain varying sizes of image projected from a stencil or matrix film 6 on the drums 19, 20 upon a sensitized sheet 57 within the casing 25, not i only will the lens carrier 64 have to be displaced but also either the sensitive sheet 57 or the stencil film 6 on the drums 19, 20.

In the arrangement shown by way of example in the drawings, the mechanism supporting the stencil film 6 has been arranged to be the second movable element and is connected to the carrier 64 by means of cam controlled toggle levers.

The carrier 64 has on its lower end a bracket 84 and also a central bracket 85 (Figures 11 and 14). The bracket 85 carries a pin 86 (Fig. 11) forming one of the pivots of a pair of levers 87, 88, the outer ends of which are in turn connected by pivots 89, 90 to a pair of levers 91, 92, the mutual pivot 93 of which is connected to a bush 94 on a slide 95 moving along guide bars 96, mounted in the bracket 25 of the flange 69 and in the casing 25 respectively. The levers 87, 8891, 92 form a pair of toggles so that the pin 93 and bush 94 are displaced according to the location of the no pin 86 and of the pivots 89, 90, which latter engage respectively inclined planes or cam surfaces 97, 98 respectively.

In order more definitely to locate the position of the carrier 64 it is preferred that the spindle 68 be driven continuously through a clutch element provided with an overload release gear or through an element such as a friction clutch capable of slipping at a predetermined load; the accurate location of the carrier 64 being obtained by the engagement of a pivoted pawl 99 (Fig. 12) on the pin 86 of the bracket 85 which engages with one or other of a number of steps or teeth 100 on a toothed cam surface of a cam drum 101 (Fig. 11) carried on a shaft 102 mounted in suitable bearings on the machine. Whenever the shaft 102 is moved clockwise the pawl 99 is swung about its pivot to operate a reversing switch reversing the drive of the shaft 74 by cutting outone of the magnetic clutch coils 80, 81 and energizing the other one. The shaft 102 is provided with means for turning it angularly within rigid but variable limits. Such means for instance, may comprise an armature 103 (Figure 42) mounted on a shaft 102 and having radial fins 104, co-operating with the poles of double magnets 105, 106, 107. Current is applied to either magnets 105, 106, or magnets 106, 107 accordin to the direction of rotation desired, the i ow of current being controlled by a commutator ring on the shaft 102 preventing the armature 103 from rotating more than one step at each current impulse.

The magnets 108, 107 are each arranged slightly out of phase with the magnet 106 as shown to make certain the direction of rotation of the armature 103, should this at any time come into position, shown in the drawing, in which a pair of fins 104 lie symmetrically with the pawls of the electro-magnet 106.

Any other means providing definite but variable location of the shaft 102 may be used.

In certain cases depending on the characteristics of the lens element used in the optical projection system, the pin 93 will not require to be moved constantly forward with the continued forward motion of the pin 86, but after a certain position is reached will be required to be moved backwards at a variable rate during the further forward progress of the pin 86. This is obtained by providing cam surfaces 108, 109 (Fig. 11) adapted to come into contact with and operate the inward motion of the levers 87, 88, and thus displace the pin 93 backwards.

Springs or weights (not shown) are provided to hold the parts up to their working positions.

Uontrol of carriage displacement for varying size of character The bracket 84 on the carrier 64 has a rack 110 (Figs. 3 and 14) on it engaging with the pinion 111 on a spindle 112 which has a. pinion 113 engaging a rack 114 (Figures 15-17). The rack 114 has a guide groove cut in it to receive a cross slide 115 carrying a knife edge 116. The slide 115 is slotted to form a guide for a bar 117, the said bar being connccted to the slide which in turn carries the magnet 190".

The knife edge 116 co-operates with one side of a curved cam lever 118 pivoted to the machine base, the other curved cam surface of which lever co-operates with a knife edge 119 on a head 120 on the spindle 121 which spindle 121 is capable of reciprocation between precisely accurate but differing set limits. It will consequently be seen that by a relative displacement of the knife edges 116, 119 any amount of displacement of the spindle 121 can be accurately multiplied or divided by any ratio and increase in size determined by the ratio of optical magnification obtained by the setting of the carrier 6-1 and light rojection element 15, as hereinbefore described Setting mechanism .magnets 126. These end flanges also carry a cross spindle 127 supporting a plurality (four in the present instance) of pawls 128 having extension levers 129 controlled by springs 130 to normally lie with their teeth out of contact with the respective ratchet rings 131 four in number, each having a key 132 (Fig. 21) sliding in a groove in bushes 133, (Figs. 23 and 24) which bushes are recesse'l to receive sleeves 135, and have cam teeth 136 on one face, the front and rear edges 137, 138 of which respectively are ground with extreme accuracy, as these provide the set limits for displacement of the spindle 121 in the particular construction shown, each having surfaces 137, 138 set at extremely accurate displacements to one another, these displacements differing for each of the bushes 133. These surfaces at the cams 136 co-operate with pins 139 on bushes 140, which slide along a key-way on the spindle 121.

Should any one of the four magnets be energized by way of example, the arm 129 and the pawl 128 will be lifted to bring the pawl into range of the teeth surface of the ring 131, so that on reciprocation of the flanges 124 from the shaft 122 the spindle 121 will be displaced against the spring 141 by a precisely accurate amount determined by the distance between the precisely ground surfaces 137, 138 of the sleeve 135 corresponding with this particular ring.

It will be understood that if any one of the electromagnets 126 is energized, the respective lever and pawl 128, 129 is moved so that upon the reciprocation of the shaft 122, the ring 131 will be rotated through a fraction of a revolution, whereby the pin 139 of the respective bushing 140 is caused to move from the low surface 137 to the high surface 138, with an endwise displacement of the respective bush 140 corresponding to the distance between these surfaces 137, 138. This causes a displacement of all of the corresponding members 133, 135, 140 toward the right in the figures, with a final movement 

